1. Field of the Invention
This invention relates to a rubber composition comprising a diene rubber, a filler and a softening agent, and a tire using such a rubber composition and a method of producing the rubber composition, and more particularly to a rubber composition for tires suitable in high-speed running such as high-performance automobile tires, racing tires and the like.
2. Description of Related Art
In automobiles for racing, the speeding up is recently made as seen in the renewal of lap time because the improvement is conspicuous in view of engines, chassis and aerodynamic technology. Similarly, high performance and speeding up are proceeding in general passenger cars.
Performances required for each tire become severer with the high performance and speeding up of a vehicle body. Among them, the improvement of high-speed durability and the improvement of gripping property on a wet road surface (hereinafter referred to as wet gripping property) are very important in view of a safeness.
It is known that the wet gripping property is improved by compounding silica instead of carbon black widely and usually compounded in the rubber composition for the tire. In tires mainly used for the purpose of running at a high speed such as running on a circuit course or the like, there is disclosed a rubber composition containing not less than 100 parts by mass based on 100 parts by mass of a rubber component. For example, there is proposed a tread rubber composition for racing tire compounding 100-250 parts by mass in total of a filler inclusive of not less than 20 parts by mass of silica and 5-50 parts by mass of a factice for providing an excellent wet gripping property and coping with adhesion at a production step (see, for example, JP-A-10-152583).
Also, there is proposed a rubber composition comprising 5-30 parts by mass of aluminum hydroxide, 40-150 parts by mass of silica and 0-100 parts by mass of carbon black to a specified rubber component, provided that a total amount of silica and carbon black is 45-165 parts by mass, and 50-200 parts by mass of a softening agent for rubber and 3-20% by mass of a silane coupling agent to silica in order to establish the wet gripping property and the wear resistance (see, for example, JP-A-2000-159935).